Our recent studies have shown that human neutrophils exposed to chemotactic factors in vivo or in vitro show enhanced chemiluminescence activity, enhanced superoxide anion generation, and increased bactericidal activity. Studies will be conducted to determine the mechanism of activation and attempts will be made to block this activation. Additional studies show that chemotactic factor can stimulate human PMNs to kill tumor cells in vitro. This area is under investigation to determine the mechanism of killing, the nature of the chemotactic factor stimulation and its potential as a modulator of tumoricidal activity in vivo. Finally, studies showing that human B and T lymphocytes respond to chemotactic factors in vitro have been performed and indicate that T cells and B cells can respond to different chemotactic stimuli. Further studies are underway to delineate these responses and determine how they may be regulated in vitro.